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Discovery of Fractionalized Neutral Spin-1/2 Excitation of Topological Order

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Chinese Physics Letters 2017年第9期34卷 1-2页

作者： Xiao-Gang Wen Department of Physics Massachusetts Institute of Technology Cambridge Massachusetts 02139 USA

After the discovery of fraction quantum Hall states in the 1980s, it became more and more clear that Landau symmetry breaking theory does not describe all possible quantum phases of matter. The new quan- tum phases of matter were called topologically ordered phases（for gapped cases） or quantum ordered phases （for gapless cases）, which correspond to pat- terns of many-body entanglement. One may won- der： besides quantum Hall systems, are there other systems that realize the new topological/quantum order？

关键词： Discovery of Fractionalized Neutral Spin-1/2 Excitation of Topological Order

TWO MODELS FOR ROLL WAVES IN A MUD LAYER

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Journal of Hydrodynamics 1995年第2期7卷 1-16页

作者： Chiang C. Mei Ko-fei Liu Chiu-on Ng(Department of Civil and Environmental Engineering massachusetts Institute of Technology,cambridge,MA USA) massachusetts Inst of Technology Cambridge United States

As has been extensively reported by hydraulic engineers in China, the flow of hyperconcentrated fluid mud in rivers is often pulsating and appears as roll waves. We report here two theories for such pulsating flows besed on two constitutive laws: the power law and Bingham plastic law. In order to account for the nonlinear bores convective inertia is kept in the approximate long wave equations. Kar man's momentum integral method with an assumed velocity profile is then employed. Results of the linearized instability analyses are *** bores are obtained either as stationary wave solutions or as the long- time limit of unstable disturbances which are initially infinitesimal. Implications on ho scour is examined.

关键词： hyperconcentrated fluid mud pulsating flow power law Bingham plastic Law

Pleistocene glaciation advances the cryptic speciation of Stellera chamaejasme *** a major biodiversity hotspot

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Journal of Integrative Plant Biology 2024年第6期66卷 1192-1205页

作者： Santosh Kumar Rana Hum Kala Rana Jacob BLandis Tianhui Kuang Juntong Chen Hengchang Wang Tao Deng Charles C.Davis Hang Sun CAS Key Laboratory for Plant Diversity and Biogeography of East Asia Kunming Institute of BotanyChinese Academy of SciencesKunming 650201China Arkansas Biosciences Institute Arkansas State UniversityJonesboroArkansas 72401USA School of Integrative Plant Science Section of Plant Biology and the L.H.Bailey HortoriumCornell UniversityIthacaNew York 14853USA BTI Computational Biology Center Boyce Thompson InstituteIthacaNew York 14853USA CAS Key Laboratory of Plant Germplasm Enhancement and Specialty Agriculture Chinese Academy of SciencesWuhan Botanical GardenWuhan 430074China Department of Organismic and Evolutionary Biology HerbariaHarvard UniversityCambridgeMassachusetts 02138USA

The mountains of Southwest China comprise a significant large mountain range and biodiversity hotspot imperiled by global climate *** high species diversity in this mountain system has long been attributed to a complex set of factors,and recent large-scale macroevolutionary investigations have placed a broad timeline on plant diversification that stretches from 10 million years ago(Mya)to the *** our increasing understanding of the temporal mode of speciation,finer-scale populationlevel investigations are lacking to better refine these temporal trends and illuminate the abiotic and biotic influences of cryptic *** is largely due to the dearth of organismal sampling among closely related species and populations,spanning the incredible size and topological heterogeneity of this *** study dives into these evolutionary dynamics of speciation using genomic and ecomorphological data of Stellera chamaejasme *** identified four previously unrecognized cryptic species having indistinct morphological traits and large metapopulation of evolving lineages,suggesting a more recent diversification(~2.67-0.90 Mya),largely influenced by Pleistocene glaciation and biotic *** factors likely influenced allopatric speciation and advocated cyclical warming–cooling episodes along elevational gradients during the *** study refines the evolutionary timeline to be much younger than previously implicated and raises the concern that projected future warming may influence the alpine species diversity,necessitating increased conservation efforts.

关键词： cryptic speciation glacial-interglacial Hengduan Mountains north-south migration Stellera chamaejasme

Stress-state dependence of dynamic strain aging:Thermal hardening and blue brittleness

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 854-866页

作者： Wen-qi Liu Jun-he Lian Advanced Manufacturing and Materials Department of Mechanical EngineeringAalto UniversityPuumiehenkuja 302150 EspooFinland Impact and Crashworthiness Lab Department of Mechanical EngineeringMassachusetts Institute of Technology77 Massachusetts AvenueCambridgeMA 02139-4307USA

This study aims to discover the stress-state dependence of the dynamic strain aging(DSA)effect on the deformation and fracture behavior of high-strength dual-phase(DP)steel at different deformation temperatures(25-400°C)and reveal the damage mechanisms under these various *** achieve different stress states,predesigned specimens with different geometric features were *** electron microscopy was applied to analyze the fracture modes(e.g.,dimple or shear mode)and underlying damage mechanism of the investigated *** is present in this DP steel,showing the Portevin-Le Chatelier(PLC)effect with serrated flow behavior,thermal hardening,and blue brittleness *** show that the stress state contributes distinctly to the DSA effect in terms of the magnitude of thermal hardening and the pattern of blue *** low stress triaxiality or Lode angle parameter promotes DSA-induced blue ***,the damage mechanisms also show dependence on the stress states in conjunction with the DSA effect.

关键词： dynamic strain aging effect Portevin-Le Chatelier effect damage mechanism dimple fracture shear fracture dual-phase steel

Environmental standards and beneficial uses of waste-to-energy(WTE)residues in civil engineering applications

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Waste Disposal and Sustainable Energy 2023年第3期5卷 323-350页

作者： Yixi Tian Shengwei Dai Jianfeng Wang Department of Materials Science and Engineering Massachusetts Institute of Technology77 Massachusetts Avenue CambridgeCambridgeMA02139USA Department of Chemical Engineering Columbia UniversityNew YorkNY10027USA Department of Earth and Environmental Engineering Columbia UniversityNew YorkNY10027USA

The waste-to-energy(WTE)technologies are now recovering energy and materials from over 300 million tonnes of municipal solid wastes *** studies have investigated substituting natural construction materials with WTE residues to relieve the environmental cost of natural resource *** study examined the beneficial uses of WTE residues in civil engineering applications and the corresponding environmental standards in Europe,the U.S.,and *** review presents the opportunities and challenges for current technical approaches and the environmental standards to be met to stabilize WTE *** principal characteristics of WTE residues(bottom ash and fly ash)and the possible solutions for their beneficial use in developed and developing countries are *** leaching procedures and environmental standards for pH,heavy metals,and polychlorinated dibenzo-p-dioxins/furans(PCDD/Fs)are *** current practice and engineering properties of materials using WTE residues,including mixtures with stone aggregate or sand,cement-based or hot-mix asphalt concrete(pavement),fill material in the embankments,substitute of Portland cement or clinker production,and ceramic-based materials(bricks and lightweight aggregate)are comprehensively reviewed.

关键词： Waste-to-energy(WTE) Bottom ash Fly ash Construction building materials Civil engineering applications Leaching standards

Quantifying Electronic Effects in QM and QM/MM Biomolecular Modeling with the Fukui Function

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物理化学学报 2018年第1期34卷 81-91页

作者： QI Helena W. KARELINA Maria KULIK Heather J. Department of Chemical Engineering Massachusetts Institute of Technology Cambridge MA 02139 USA. Department of Chemistry Massachusetts Institute of Technology Cambridge MA 02139 USA.

Multi-scale quantum-mechanical/molecular-mechanical(QM/MM) and large-scale QM simulation provide valuable insight into enzyme mechanism and structure-property relationships. Analysis of the electron density afforded through these methods can enhance our understanding of how the enzyme environment modulates reactivity at the enzyme active site. From this perspective, tools from conceptual density functional theory to interrogate electron densities can provide added insight into enzyme function. We recently introduced the highly parallelizable Fukui shift analysis(FSA) method, which identifies how frontier states of an active site are altered by the presence of an additional QM residue to identify when QM treatment of a residue is essential as a result of quantum-mechanically affecting the behavior of the active site. We now demonstrate and analyze distance and residue dependence of Fukui function shifts in pairs of residues representing different non-covalent interactions. We also show how the interpretation of the Fukui function as a measure of relative nucleophilicity provides insight into enzymes that carry out S_N2 methyl transfer. The FSA method represents a promising approach for the systematic, unbiased determination of quantum mechanical effects in enzymes and for other complex systems that necessitate multi-scale modeling.

关键词：《物理化学学报》期刊编辑工作发行工作

GPS monitoring of the crustal motion in southwestern China

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Chinese Science Bulletin 1999年第19期44卷 1804-1807页

作者： B.Clark Burchfiel Robert W.King Leigh H.Royden massachusetts Institute of Technology CambridgeMA 02139USAMassachusetts Institute of TechnologyCambridgeMA 02139USAMassachusetts Institute of TechnologyCambridgeMA 02139USA

Through GPS carrier phases observation in southwestern China during 1991-1997,the velocity field within eastern Qinghai-Xizang (Tibet) and its neighbour regions has been es-’tablished. The velocity of those sites in and west of Chuan-Dian block is mostly 5-10 mm·a-1relative to the fiduciary station CHDU (Chengdu), and the motion in Chuan-Qing and

关键词： eastern Tibetan Plateau global positioning system (GPS) crustal motion and deformation.

Direct optical-structure correlation in atomically thin dichalcogenides and heterostructures

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Nano Research 2020年第5期13卷 1363-1368页

作者： Akshay Singh Hae Yeon Lee Silvija Gradcak Department of Materials Science and Engineering Massachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02141USA

Atomically thin transition metal dichalcogenides(TMDs)have distinct opto-electronic properties including enhanced luminescence and high on-off current ratios,which can be further modulated by making more complex TMD ***,resolution limits of conventional optical methods do not allow for direct nanoscale optical-structural correlation measurements in these materials,particularly of buried interfaces in TMD *** we use,for the first time,electron beam induced cathodoluminescence in a scanning transmission electron microscope(CL-STEM)to measure optical properties of monolayer TMDs(WS2,MoS2 and WSSe alloy)encapsulated between layers of *** observe dark areas resulting from localized(~100 nm)imperfect interfaces and monolayer folding,which shows that the intimate contact between layers in this application-relevant heterostructure is required for proper inter layer *** also realize a suitable imaging method that minimizes electron-beam induced changes and provides measurement of intrinsic *** overcome the limitation of small electron interaction volume in TMD monolayer(and hence low photon yield),we find that encapsulation of TMD monolayers with hBN and subsequent annealing is ***-STEM offers to be a powerful method to directly measure structure-optical correspondence in lateral or vertical heterostructures and alloys.

关键词： cathodoluminescence two-dimensional(2D)materials transition metal dichalcogenides interfaces heterostructures

Abnormal nonlinear optical responses on the surface of topological materials

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npj Computational Materials 2022年第1期8卷 1045-1052页

作者： Haowei Xu Hua Wang Ju Li Department of Nuclear Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA Department of Materials Science and Engineering Massachusetts Institute of TechnologyCambridgeMA02139USA

The nonlinear optical(NLO)responses of topological materials are under active *** previous works studied the surface and bulk NLO responses *** we develop a generic Green’s function framework to investigate the surface and bulk NLO responses *** reveal that the topological surface can behave disparately from the bulk under light ***,the photocurrents on the surface can flow in opposite directions to those in the bulk interior,and the light-induced spin current on the surface can be orders of magnitude stronger than its bulk counterpart on a per-volume *** also study the responses under inhomogeneous field and higher-order NLO effect,which are all distinct on the *** anomalous surface responses suggest that light can be a valuable tool for probing the surface states of topological ***,the surface effects should be prudently considered when investigating the optical properties of topological materials.

关键词： materials. surface. topological